Hierarchical Ray Tracing With Cached Instance Transforms
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Solution Overview
Problem
Ray tracing systems face challenges in achieving real-time rendering on devices with tight constraints on silicon area, cost, and power consumption, such as mobile devices, due to high processing requirements and inefficient intersection testing with current acceleration structures.
Innovation Solution
A hierarchical acceleration structure with instance transforms is used, where each lower level node has a defined relationship to an upper level node, and an instance transform cache stores these transforms for efficient retrieval during intersection testing, reducing memory access overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hierarchical acceleration structure is used for intersection testing, then the processing efficiency is improved, but the memory access overhead increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing instance transforms in a cache before intersection testing begins. This allows the ray tracing system to quickly retrieve transformation matrices during rendering without performing redundant calculations, thereby reducing memory access overhead while maintaining improved intersection testing efficiency through the hierarchical acceleration structure.
Solution Approach 2:
The patent uses copying by creating a cached copy of instance transforms that can be quickly accessed during intersection testing. Instead of repeatedly accessing or recalculating transformation data from the original hierarchical structure, the system maintains optimized copies in memory, reducing the time penalty associated with memory access while preserving the benefits of hierarchical organization for intersection testing.
2Manufacturing precision
If ray tracing is implemented on mobile devices with tight constraints, then photorealistic rendering is achieved, but power consumption and silicon area increase
Solution Approach 1:
The patent applies segmentation by dividing the ray tracing workload into manageable components through the hierarchical acceleration structure. By organizing primitives into nested bounding volume hierarchies and processing rays in structured batches, the system reduces the overall computational complexity, enabling photorealistic rendering on mobile devices while managing power consumption through efficient task division and parallel processing.
Solution Approach 2:
The patent uses parameter changes by optimizing the hierarchical acceleration structure parameters specifically for mobile rendering constraints. This includes adjusting bounding volume hierarchies, instance transform caching strategies, and ray batch sizes to balance rendering quality with power consumption, allowing photorealistic output on resource-constrained devices through parameterized optimization rather than brute-force computation.
3Loss of time
If instance transforms are cached for lower level nodes, then memory access is minimized, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the instance transform cache to serve multiple functions within the ray tracing pipeline. The cache structure not only stores transformation matrices for quick access but also implicitly manages hierarchical node relationships and supports various levels of the acceleration structure, thereby minimizing memory access time while avoiding the need for separate dedicated structures for each function, thus controlling device complexity.
Data Source
AI summary
A system and method for coherency gathering for rays in a ray tracing system. The ray tracing system uses a hierarchical acceleration structure comprising a plurality of nodes including upper level nodes and lower level nodes. For each instance where one of the lower level nodes is a child of one of the upper level nodes, an instance transform is defined, specifying the relationship between a first coordinate system of the upper level node and the second coordinate system for that instance of the lower level node. The system provides an instance transform cache for storing a plurality of these instance transforms while conducting intersection testing.